The present invention relates to a vibration pickup with a pressure sleeve.
Vibration pickups of the above mentioned general type are known in the art. One of such vibration pickups with a pressure sleeve is disclosed for example in the German patent document DE 195 24 147.9. It is formed as a knock sensor for monitoring the operation of an internal combustion engine in a motor vehicle. The pressure sleeve is joined through an abutment region fixedly to a component which causes vibrations, for example a motor block of the internal combustion engine.
The vibrations to be detected are knock noises of the internal combustion engine during the operation. They are transmitted through a pressure sleeve to a piezo-ceramic disk as a sensor element, with intermediately located contact disks and insulating disks which allow picking up of a signal, so as to form an evaluatable electrical output signal.
This type of mounting or clamping of the sensor element on the pressure sleeve and the mounting of the pressure sleeve on the vibrating component has a great influence on the manufacture. The clamping of the sensor element together with a plurality of individual components, for example with a spring and a seismic mass is performed in the known vibration pickup with a threaded ring which is screwed on the corresponding thread of the pressure sleeve and directly abuts on the seismic mass.
The clamping of the components on the pressure sleeve is a substantial cost factor. All components must be firmly compressed with a defined mechanical pre-tensioning and remain so. When the pre-tensioning changes, also the transmission characteristic line changes and the evaluation becomes more difficult.